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  1. #26
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by wilde1j View Post
    Unless you have the tools and skills to properly measure the bores, let the machine shop tell you the OS to get. Just tell them you will use brand "x" pistons. Once they measure, they should recommend the smallest OS that will allow proper bore cleanup.

    Bearings are readily available.

    If you don't have one, now would be a good time to get an OEM shop manual.
    thanks jim for the valuable information about piston sizing, i would of never of thought that.
    i hear ya jim, if i didnt have the oem manual, i would be stripping bolts off the motor and would be still on the lower unit.

  2. #27
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by Jayrock View Post
    I used to use a Carbide Ball shaped deburring bit, Carbide cone deburring bits work good too, but they are spendy. So, Its not exactly a Ball hone that I use now. I use a cone shaped sanding bit that Dremel Makes. I paid less that 10 bux for the one I have now, and I have used it several times.
    fantastic idea, now i have a reason to use that sanding bit!

  3. #28
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    Default Re: opinions on what to do about scratches inside piston wall

    Jayrock, i like how you think. toast to you bro. if i was close down to diego i would definately buy you a drink. i will try the local craigslist, no sense in spending more cash than i have too and i can spend more time with the family.
    i went by to that local machine shop and they only do cars.
    anybody tried sending their powerheads out to get them rebored and pistoned up? any good shops out there that do this?

  4. #29
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    Default Re: opinions on what to do about scratches inside piston wall

    I stripped my block which only had one out of round piston. but the bore was right at max spec, and you always need to hone to get the rings to seat...so I went .020 over size on all cylinders...because for all the work I am doing , I dont want it to bite me in the behind, because i tried to save $200 someplace..

    I sent my block to Lashelle Engine Restorations( freeport lll). I actually got the number from a palce that didnt really want to do my block, and mention that he sends all his blocks out...so i asked who.. this was the guy.. It came back really nice( i have the measuring equipment and tools to know!!) I am thinking that a bore and hone was about $40 per hole...

    but you can ask him... he had already done hundreds of 60 degree blocks like mine...which are a little tricky with that flat bottom bore!! need special hones to do blocks like these.


    good luck

    bob

  5. #30
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    Default Re: opinions on what to do about scratches inside piston wall

    I rebuilt my own 60hp this last summer. The only tool I don't have is the mill for boring so I had a local machine shop do that work. Once I got it back I brought the cylinders up to size with the hones. Then debured all the ports, debured the pistons, cleaned everything up and assembled. I have ran 3 tanks of gas threw the motor already and everything is working great! The pistons are .020 over. We got the motor in to be a parts motor for our 70hp on the work boat but the only parts we ever needed off this motor was the trim relays. lol

    We got this 60 without a head and all 3 pistons and cylinders were scored from heat. It was a very fun build and I think I have $300 total in the motor with new pistons, head, and complete gasket set.

    I just posted a couple pics here: http://forums.iboats.com/johnson-evinrude-outboards/need-adjustment-carbs-95-omc-70-hp-97206.html

  6. #31
    Petty Officer 1st Class DargelJohn's Avatar
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    Default Re: opinions on what to do about scratches inside piston wall

    Off subject a little... But I have been recently told by a professional engine builder and a manufacuturing rep for an aftermarket piston kit company, that as long as the machine shop does their job properly, you do not have to worry about piston or ring end gap clearances. Pistons and rings are built to very exacting tolerances these days.

    For Example: Let's say your Standard Bore Size is 3.500" and you want to bore it out to 3.530" (.030 oversized). As long as the machine shop bores the cylinders to that spec, the .030 piston kits will work.

    My engine rebuild turned out perfect, without supplying the piston kit to the machine shop. I was also advised to use cast piston and not forged. Forged are made of harder metal and can damage the cylinders more during a failure.

    Just my expierence.
    "A life without risk is not a life." -unknown-

  7. #32
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by snowseeker View Post
    I rebuilt my own 60hp this last summer. The only tool I don't have is the mill for boring so I had a local machine shop do that work. Once I got it back I brought the cylinders up to size with the hones. Then debured all the ports, debured the pistons, cleaned everything up and assembled. I have ran 3 tanks of gas threw the motor already and everything is working great! The pistons are .020 over. We got the motor in to be a parts motor for our 70hp on the work boat but the only parts we ever needed off this motor was the trim relays. lol

    We got this 60 without a head and all 3 pistons and cylinders were scored from heat. It was a very fun build and I think I have $300 total in the motor with new pistons, head, and complete gasket set.

    I just posted a couple pics here: http://forums.iboats.com/johnson-evinrude-outboards/need-adjustment-carbs-95-omc-70-hp-97206.html
    you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

    Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

    bob

  8. #33
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by apollothesun View Post
    Jayrock, i like how you think. toast to you bro. if i was close down to diego i would definately buy you a drink. i will try the local craigslist, no sense in spending more cash than i have too and i can spend more time with the family.
    i went by to that local machine shop and they only do cars.
    anybody tried sending their powerheads out to get them rebored and pistoned up? any good shops out there that do this?
    Marine Machine shops:
    Mar Fab -- talk to Kurt or Dan at 931-738-2815 (Tennessee)

    Flagship

    Tribble

    Blackburn

    Roehrs

    Riverside

    You might also consider buying a rebuilt powerhead (iboats has them). They typically come with a warranty as well. I would strongly recommend against anything but a marine machine shop. The others don't have the experience or the fixtures to do it right. The good shops are up on service bulletins and fixes to give you a long lasting job.
    Jim

    ===============================
    I don't respond to Private Messages PM's that are motor questions.

    For basic information on a wide range of topics, see Top Secret File
    Link: http://forums.iboats.com/johnson-evinrude-outboards/top-secret-file-updated-8-1-2012-a-299680.html

    OEM shop manual: outboardbooks.com or Ebay

  9. #34
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    Default Re: opinions on what to do about scratches inside piston wall

    thanks Bob, Jim, Snowseeker and Dargeljohn for the treasure trove of information.
    i was up late last night hunting for a engine in hopes for a replacement.
    i got a reply about an 85hp 1976 that can replace my existing motor which i can sell my motor for parts. he's asking $650, 120psi on all cylinders, new water pump recently serviced. sounds like a good deal. although my wife has to hear about the cost cuz my allowance cant afford paying for that right now.
    i called around this morning for shops that do reboring and all 3 say they send them to one place up north. i called the shop and talked to dale and was very helpful and eager to help me. he said he can do $50 a bore and readily has pistons availble for replacement. i feel confident about this transaction.
    so, what do you guys think,
    if i can get the boring done for 50, 150 for piston and rings, 50 bucks for another set of rings for the other pistons, powerhead gasket set 100, maybe two weekends to put it all together totaling about 350.
    or go with the 85hp, less horsepower, double the cost, although more time with the family
    gonna have to weigh on the thoughts till the end of the day.

  10. #35
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by bob johnson View Post
    you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

    Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

    bob

    Everything was from ebay. I may have stretched the total a bit but it for sure was not over $400. I believe the pistons were $50 each with rings and pins, gasket set was $55, head was $65, and thermostat and cover were $25. The head was not new.

  11. #36
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by bob johnson View Post
    you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

    Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

    bob
    Now Bob.... I thought I gave you a heck of a deal on your parts even the new S/S mounting bolts. You still need a rectifier/reg???
    When in doubt,Trim it out!!!
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  12. #37
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    Default Re: opinions on what to do about scratches inside piston wall

    well i dropped the block off this weekend and got a reply back from the machinist today.
    he says that piston 4 needs to be bored to .040
    that size because the ports already at .030
    the other ports are okay but recommends piston 3 be rebored too
    he says if he cant bore .040 then he wont charge me, and suggests a resleeve which is about 220.

    looking closer at the pistons over the weekend looks like piston 2 and 3 need to be replaced. some scratches that can be felt with the finger nail.
    what happens to the scratches? does it overheat the piston walls? can the scratches be smoothed down with a dremmel and sanding bits? or is that asking for trouble

    if i do rebore all the ports,
    thats about 100 per piston plus 50 per bore totalling about 600 not including rings.
    man, i dont think its worth it.
    the boat is a 1977 apollo ski boat. the boats in decent shape and so is the trailer.
    what kind of resale would i get if i do a complete rebuild on the motor?

    what if i go ahead on the rebore on piston number 4, find used pistons for 2 and 3 and put it all back together. how long do you think its gonna last?

    wouldnt it be cheaper to resleeve all the ports and get pistons for them?

    last option would be to part it all out and use the funds for a new motor.

  13. #38
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by Faztbullet View Post
    Now Bob.... I thought I gave you a heck of a deal on your parts even the new S/S mounting bolts. You still need a rectifier/reg???
    no doubt at that moment in time you were king!!!.. and since you cherish that so much, the next time i need new pistons and a NEW HEAD and gaskets lets remember this conversation and ill send a check for $301!!!!!!! ha ha ha

    wait... I dont want a next time!!!!!!!!!! ha ha ha

    I am going to need another rectifier-reg for sure...but I wont need it till summer i guess.. I might need a few more things as well...

    things picking up in your place yet????? got to be some stirring of the fishermen down your way by now!

    bob

  14. #39
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    Default Re: opinions on what to do about scratches inside piston wall

    got off the phone with the machinist this morning and had to bore cylinders 3 and 4 to
    .040
    i asked to see if i can get away with piston 1 and 2 for a while but he said im gonna need new piston heads.
    so, im looking for some pistons 2 X .040 and 2 X .030
    wiseco pistons were coming at 100.00+ but includes wrist pins and bearings
    trying to find a pair of good .030 pistons

    hey bob, i see you were in my shoes sometime last year,
    http://forums.iboats.com/johnson-evinrude-outboards/slight-piston-damage-opinions-please-373454-2.html
    how did you fare with that 80hp motor? any parts for sale?

  15. #40
    Petty Officer 2nd Class Jayrock's Avatar
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by apollothesun View Post
    got off the phone with the machinist this morning and had to bore cylinders 3 and 4 to
    .040
    i asked to see if i can get away with piston 1 and 2 for a while but he said im gonna need new piston heads.
    so, im looking for some pistons 2 X .040 and 2 X .030
    wiseco pistons were coming at 100.00+ but includes wrist pins and bearings
    trying to find a pair of good .030 pistons

    hey bob, i see you were in my shoes sometime last year,
    http://forums.iboats.com/johnson-evinrude-outboards/slight-piston-damage-opinions-please-373454-2.html
    how did you fare with that 80hp motor? any parts for sale?
    You will probably have to stick with Wiseco bro. It is not wise to use pistons of different makes in the same engine. They might not weigh the same. I am surprised the machinist did not mention this too you.

  16. #41
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    Default Re: opinions on what to do about scratches inside piston wall

    i didnt know that all the pistons had to be the same make.
    thanks jayrock, i will go foward in getting all pistons the same make.

    okay,
    i was looking for omc pistons .040 for my engine, and im having a hell of a time trying to get a serial or model number
    the sierra pistons are 78.00 a piece.
    any word about sierra replacement part pistons? are these decent pistons?
    the wiseco are about 100.00 a piece.

    now im thinking i should just get all the holes bored and save up for the .040 pistons

  17. #42
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    Default Re: opinions on what to do about scratches inside piston wall

    OEM# 396588, 396504, 327861, 317831
    for omc .030

    OEM # 438998, 439002, 327861, 317831
    for omc .040

  18. #43
    Fleet Admiral Faztbullet's Avatar
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    Default Re: opinions on what to do about scratches inside piston wall

    didnt know that all the pistons had to be the same make.
    They dont, the oversize piston weighs the same as a stock piston no matter what brand. If you need new .030's or .040's pm me. I sell a cast piston that identical to the OEM stock and they are less than $65 each.
    When in doubt,Trim it out!!!
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  19. #44
    Petty Officer 2nd Class Jayrock's Avatar
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    Default Re: opinions on what to do about scratches inside piston wall

    Quote Originally Posted by Faztbullet View Post
    They dont, the oversize piston weighs the same as a stock piston no matter what brand. If you need new .030's or .040's pm me. I sell a cast piston that identical to the OEM stock and they are less than $65 each.
    Umm, Not always. Wiseco forged are known to me to be a little heavier than an OMC cast piston of the same size. Did this change all of a sudden?

  20. #45
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    Default Re: opinions on what to do about scratches inside piston wall

    so is the verdict out? is it okay to mismatch pistons in a block? i tried doing a search on it and didnt find information on it.

    also, with my particular engine, it doesnt matter if the piston head is port or starboard correct? when i was looking for pistons, i saw on the other model engines that you had to get either the port or starboard piston. looking at my pistons, they all look the same. just got to make sure its the correct size and oem model cross-match, correct? meaning cross flow, V-4, 90 degree year and hp, right?


    hey faztbullet, i will be pm'ing when i get my block this weekend. thanks for the heads up.

  21. #46
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    Default Re: opinions on what to do about scratches inside piston wall

    I dont KNOW for sure, but my brain is telling me , that you should not mix FORGED pistons with CAST pistons..... I think they expand differently...but it might not matter because the fit is between the cylinder and its own piston

    Apollo: that motor is still on hold... it is torn down, cleaned up and ready for assembly for the most part... I still have not bought the piston though. I have sand blasted most of the parts and painted...it looks good sitting on the floor in pieces!! ha ha ha


    dont know what i am going to do with it...got a bunch of projects before it

    bob

  22. #47
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    Default Re: opinions on what to do about scratches inside piston wall

    Can you just find a good used power head?

  23. #48
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    Default Re: opinions on what to do about scratches inside piston wall

    hey snowseeker,
    yeah, been searching around, found a used complete 85hp evinrude for $600 but for that much and the lower hp i decided to go forward on rebuilding the 115hp.

    after the fact i already got the cylinders bore, i saw this website
    http://shipwrecksalvage.net/cart/joh...ock-p-736.html
    oh well, my luck i guess. figuring shipping and getting the cylinders honed probably 500 delivered to my door.

    so far, i got cylinder 3 and 4 bore to .040. $50.00 a bore. at least the new bores will be both out of the bottom block. i won some piston heads on ebay today, 2X .030 for cylinders 1 and 2. got a good deal too, 50 bucks for both
    they are omc pistons.
    i will contact faztbullet for the .040 pistons this weekend.

    so right now, i currently got 200.00 in the rebuild so far.
    this is actually a fun rebuild, i got a chance to know you guys and answerd alot of my questions i had in the process. this experience so far will help me in the upcoming years of boating.

    i have a question about gaskets.
    been shopping around for powerhead gasket set for my motor and saw the prices. im almost thinking about making gaskets myself. i made gaskets for a mercury 3.9hp and worked great. although it was a small motor, they were easily traced and cut. now since i have the engine apart for the evinrude, im thinking it would be easy to trace and cut, although time would be a factor. anyways, i can do this while i wait for the parts to come through.
    the only gasket im concerned about is the cylinder head gaskets. the current ones look good still, im thinking about using them again. any objections or experience in reusing gaskets? the cylinder head gasket has some kind of metal on the inner circle, i was wondering if i made my own, is this particularly important?
    i can get a sheet from a auto shop and then sit down, trace and cut, hole punch costing me $20.00 if i buy all the gaskets for the motor, it totals out about $150.00
    probably the only gasket i would buy would be the powerhead to lower unit.
    any other gaskets i should buy that i should be aware off, or do you guys cut your own too?

  24. #49
    Fleet Admiral Faztbullet's Avatar
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    Default Re: opinions on what to do about scratches inside piston wall

    Wiseco forged are known to me to be a little heavier than an OMC cast piston of the same size. Did this change all of a sudden?
    It should be the same weight, that way you can only repair what is needed. If they are heavier that may be cause of some of their failures. I do not use or recommend Wisco pistons as they are too soft and need several heat cycles to harden them up. Also if bore is not set up for a Wiseco it will cold seize as customers will not let engines warm up. Do not not reuse the head gaskets...
    I can beat the gasket set price....with head gaskets.
    When in doubt,Trim it out!!!
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  25. #50
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    Default Re: opinions on what to do about scratches inside piston wall

    let me get my parts list going and see what you have in stock. Faztbullet, thanks once again!

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